The overall goals of this longitudinal study are to examine the etiologic determinants of adult tobacco use and dependence and the consequences of use on the individual's functioning. The original sample in 1975 consisted of 960 mothers whose children's average age was 5 (T1). Subsequently, children and their mothers were interviewed when the children's average age was 13 (T2), 15 (T3), and 21 (T4). At T5, only the young adults (average age 26) were interviewed. A sixth data collection (T6), when the participants are an average age of 33 years old, is proposed to accomplish the following: (1) to examine interrelations and interactions of personality, family, peer, and ecological factors (starting in early childhood) as they affect the course of tobacco use and dependence over time (i.e., stability, and change); and (2) to study the consequences of long-term tobacco use/dependence on adult intra- and interpersonal functioning. As in the past, separate interviews with adults will be conducted in their own homes by trained interviewers. Scales with adequate psychometric properties measuring the independent variables will be developed from the interview schedules. The primary analytic techniques will be causal analysis and/or hierarchical or logistic regression. The significance of this study lies in its longitudinal design with in-depth intra- and interpersonal data available at several crucial stages of development. These data allow us not only to examine the pathways to tobacco use and dependence from the very beginning but also to study the course of tobacco use over time, i.e., the factors related to the subject's becoming more (or less) involved in tobacco use/abuse over a span of years. We can also examine the factors related to cessation of smoking. Such knowledge will help pinpoint those adolescents/young adults/adults at risk for increased tobacco use/dependence and will provide detailed and specific guidelines for prevention and treatment. Our longitudinal study of the consequences of tobacco use is unique in that the long-term effects of use can be evaluated to see if their impact is cumulative. Identification of childhood and adolescent factors that can lessen or compensate for the impact of tobacco use on later functioning would provide additional aids for effective prevention and treatment efforts.